Conventional sorption dehumidifiers are usually regenerated in a so-called open system, i.e. the regenerating air is taken from surrounding outside air and returned to the surroundings after it has passed a sorption mass and has driven the moisture out of it.
It is often a disadvantage to need duct connection to the surroundings, and a so-called closed regeneration system is then selected, in which, after the air through the sorption mass, the regenerating air is allowed to pass a cooler or condenser, in which this air is cooled so that the absorbed moisture is dispelled before the air is taken back to the sorption mass via a heater, wherein the temperature of the regenerating air is raised to drive the moisture out of the mass. In its turn the condenser is then cooled by a secondary air stream from the dehumidified enclosure which is then in turn supplied with the heat taken from the regenerating air.
This process is also has disadvantages. One such disadvantage is that the energy requirements compared with the open system will be higher. In addition the amount of heat which is supplied to the dehumidified enclosure via the secondary air through the condenser gives the enclosure a temperature increase, which can be troublesome. In certain cases when the dehumidified enclosure, and thus also the cooling air supplied to the condenser, has a temperature lying below 0.degree. C. there is a risk that the condensate will freeze in the condensor, so that it will become blocked and no longer function.